Making lead powder



Nov. 10, 1936. s. lsHlMuRA MAKING LEAD POWDER Filed Nov.A 3,1951 2sheets-sheet 2 l nl Patented Nov. 10, 1936 ,PATENT oFFlcE MAKING LEADrownmt Lyuho S. Ishimura, Kamlkyo-Ku, Kyoto, Japan Application November3, 1931, Serial No. 572,857

13 claims.

This invention relates to the production of oxidized lead powder in anextremely dry and ne state of subdivision.

One object of the invention is to carry Aforward and improve certainfeatures disclosed in my application No. 470,652, filed July th, 1930.

lAnother object of the invention is to provide for.a supplyv ofauxiliary air to' a tumbling mill so as to control the lead oxidationand also the mill temperature without supplying additional air throughthe main branched tube nozzlesA whichv tend to blow out undesirablecoarse product.v

Another improvement in the invention relates to the nozzlecaps to beattached to the branched tube ends so as to prevent the speedingcompressed air from projecting directly against the contents so asvtoblow out any undesirable coarse powder. Another improvement in theVinvention relates to the material feeding mouth arrangement byproviding a sufcient number of control valves 'to prevent any free'airfrom entering into the mill during the feed thus isolating the mill fromatmospheric conditions in order to keep the mill at a uniformlycontrolled condition.

' 'Another object of the invention is to provid a free air intakebetween the mill discharge line and the product collecting system andcollect the produced oxide at the lowest possible temperaf ture, so a'sto avoid further rapid oxidation due to spontaneous combustion, also toprovide an air supply line between the mill and the product collectorwhereby air may `be supplied by a fan to adjust the temperature of thecollectors according to atmospheric conditions, the temperature ofwhichvaries from below Azero to 110 F.A throughout the seasons.

Another improvement in the invention relatesl to the product collectorarrangement in which the product of lead suboxide powder, or theoxidized lead containing lead suboxide, tends to catch fire byspontaneous oxidation when accumulated and subjected to elevatedtemperatures. 'Ihe present improvement avoids such accumulation at allplaces within the system and discharges the product quickly into theatmosphere vso as to bring the produced material to room temperature andthus checks further undesirable rapid oxidation.

Another improvement relates to the operation of the mill underautomatically controlled condif tions so as to cause the mill to operateat a definite desired temperature* limit.

Withwthis general statement of the objects of my invention I will nowproceed to describe the v same in connection Withthe attached drawings:

Fig. 1 is a horizontal view of my apparatus partly in section.

Fig. 2 is a. plan view of the product collectors. l Fig. 3 is aside-view Vin section showing an enlarged view of the nozzle caps to beattached to 5. theends of the branched air pipes and the generaldirection of the air issuing from' the nozzle.

Fig. 4 is a sectional ,view of the rotary lock provided at the end ofthevscrew conveyor on the lower end of the product collector of Fig. 1.

When lead oxide powder is generated from lead lumps in a tumbling mill,as disclosedin my application 470,652, much heat is generated partlyfrom chemical action and heretofore it has been desirable to water cool'the mill. My present 15 improvement largely overcomes this difficulty.

Referring more particularly to Fig. 1, around the main air supply pipeI. and extending into the mill 5 there are provlded`a number of branch 4extending from the auxiliary air pipe 2. The

idea is to prevent the tendency of air forced into the mill from backingout through the mill feeding mouth 8 carrying out into the atmosphere,iln'e lead particles, and at the same time to supply 30 additional airin any desirable quantity which is necessary to aid oxidation or toeiect the cooling of the mill in case itis necessary. The regulation ofsuch effect can be attained byadjustingI the quantity of such air passedin through the secondary supply pipe 3 connectedto the fan 21 by meansofa valve 2|.

The main advantage of this auxiliary pipe arrangement is that -itenables the control of the mill temperature without affecting theblowing 40 conditions for blowing the powder from the mill so as toobtain a fairly uniform product. Such adjustment istroublesome when allthe air passes through the main air supply pipe I because when all theair is passed through the main supply pipe I and the air increased, theincreased amount of air blowing directly against the contents afl fectsthe coarseness of the discharged product.

Referring to Fig. l, the main air supply tube I extends into the mill 5which, as shown more inV 50 detail in my aforesaid application, ismounted to revolve horizontally while enclosing the tubes 23 so as tovsupply air from the fan 21.

To the end of these branch pipes 23the nozzle caps 24, shown enlarged inFig.3, are attached so as to spread the air current without projectingit in a concentrated stream directly upon the contents. The conicalshape of the interior of the air spreading pieces 24 functions for thispurpose as shown in Fig. 3. At the same time the position of suchbranched air pipes can be adjusted to a most eilicient position by meansof the adjustinghandle 40, Fig. 1, attached to the main air line l. Theadjustment of said nozzle position is important to accord with the'speedof the mill and also the amount of contents in the The proper positionof the nozzle is shown in Fig. 3. By providing the nozzle caps, whichmay be called pressure proof caps, th'e blowing out of any coarserleaden product is prevented regardless of the change in the amount ofair supplied.

It is important at times to change the air quantity passing through themill as this air principally controls the mill temperature in accordancewith the amount of charge and also variable atmospheric temperature. Allthe air pipe lines are guarded from any air leakages by providingsuitable stumng boxes I3, Fig. l.

Referring to 1, the initial material, lead pieces or lum'ps are conveyedby a properly arranged conveyor 53 and fed into a charging mouth Il andthrough alternately swinging valves Il and I2 they are taken into themill passing through the hollow, internally screw threaded 'trunnion 1.The entire feeding operation including the valves l l and I2 is operatedby a properly arranged motorv l1 which is controlled, as hereinafterdescribed, by means of a thermostat control mechanism.

The object of having the two valves Il and I2 operating at alternateintervals is to prevent too much free air from entering the mill duringthe feed, thus isolating the system from the atmosphere, also thesevalves are advantageous for stopping the air from being blown outbackwardly in case the entire system is operated under pressure insteadof suction. An arrangement which isolates the mill system fromatmospheric variations is advantageous in order to keep the milltemperature at a uniformly controlled condition. The valves Il and I2are normally held closed by springs Il and alternately opened by camsl2' operated by the motor I1.

Referring to Fig. 1, the air passed into the mill 5 through the branchpipes 23 and also from the auxiliary air supply nozzles d dischargesthrough the outlet pipe 26 carrying with it the powder formed by theabrasive action of the lead lumps on each other, enters into an encloseddust collector 28 and after passing through dust separating bags 29, theseparated air is exhausted through a suction fan 30 having a damper 3|so as to regulate thesuction.

The fan 30 has a far greater capacity than the amount of air which canpass through the mill -and the entire product separator system, so thatunder ordinary operating condition, free air will be drawn in throughthe pipe connection 21, shown in Fig. 1, attached to the mill dischargepipe 26 between the mill 5 and the product collector 28. 'I'he amount offree air from the atmosphere can be regulated by means of a valve 32. Asthe product is discharged from the mill it consists mainly of leadsuboxide PbzO or further oxidized lead PbO having mixed with it leadsuboxide and it possesses a highly reactive nature and tends to burn toproduce an elevated heat condition, and this material must be cooleddown as soon as possible after it is discharged from the mill and as itcomes into the product separator28. Whenasuilicient amount of free airat room temperature is drawn into said separator, the entire collectorsystem will be cooled down moderately and when the collected oxide haspassed through a water cooled screw conveyor`33 arranged at the lowerVend of the separator 28 and discharged through an automatic dischargelock v34, shown in `detail in Fig. 4, it will have reached as low atemperature as the corresponding room temperature so as to check'completely further undesirable rapid oxidation.

Such oxide product containing lead suboxide always tends to startcombustion due to spontaneous oxidation when it is accumulated andsubjected to an elevated heat condition, and it is desirable not toaccumulate this powder and also to avoid subjecting it beyond a certaintemperature limit.

The separation bags 29 provided in the product collector 28 are arrangedto vibrate so as to shake down the bags at frequent intervals. 'I'heoperation alternately takes place in two or more product collectors,Fig. 2, and during such shaking period the valves 38 provided in thedischarge pipe 26 to the collectors are arranged tobe closed in ordertosecure the alternate operation effec-4 tively, by stopping the airpassing through these bags, but at the same period another air supplyline 31, Fig. l, having a mechanically operated valve 39 is opened forair and allows air to enter the compartments formed by an upperperforated shelf 36 and lower imperforate parts 35 provided to beslipped over the lower ends of tubes 29 and secure the lower edge ofsaid dust bags to the tubes, and the air is blown through the holesprovided on the upper shelves. The idea is to prevent iine reactivepowder accumulating upon such spaces after it has passed through thebags, as such accumulation might start a re due to spontaneousoxidation, while if there was no air current within the system,especially along the outside of the dust bags, the ne powder sticking onthe outside of said bags will fall down during the shaking period andwould accumulate gradually so as tol start spontaneous oxidation. Theair current passing over the outside of the bags carries away nedangerous oxide powder.

The suction fan 30 discharges the separated air from the system and itseffects can be adjusted by the attached damper 3| so as to regulate theextent of the suction.

A water cooled screw conveying arrangement 33, Fig. 1, -is provided atthe lower end of the product collector and the product is dischargedfreely into the atmosphere by means of a rotary lock 34, as shown inFig. 1 and Fig. 4. Thus my present arrangement may discharge the productof a highly reactive nature quickly and at a low temperature withoutundue accumulationof the product within the collector system.

Referring to Fig. l, a motor Il diagrammatically shown attached to thelead lump feed mechanism 56, may be provided with a thermostatarrangement 'directly controlled by a pyrometer A having a thermocoupleB installed in the mill 5 so that said motor can be automaticallycontrolled within speciiied temperature limits. That is, when themill'temperature reaches its lower limit the pointer C contacts anadjustable I,

charge, while if the temperature passes beyond pally on its operatingtemperature, but this mill temperature can lead pieces charged in themill v tion, is directly lead be attained by regulation of the quantityof and also by the amount of air passing through the mill. That is, theheat generation due to the friction 'of the charged mass' and theoxidaproportional to the vamount of lead pieces, charged in the mill andunder a denite amoot of air which passes through the mill, the ope` t ngtemperature of the mill can be controlled by only adjusting the amountof charge in the mill. \Gonsequently by means of the feed motor,controlledby the thermostat arrangement shown, thel mill temperature canbe maintained automatically at a desired range, so as to produce acertain kind of oxidized lead product.

It is rimportant that according to the range of ,the operating milltemperature the product may be straight litharge PbO, lead suboxidePbzO,

red lead PbzOa, metallic lead powder Pb, or -mixtures of above mentionedtwo or three substancesI in various proportions besides containingpossibly some other form of oxidized lead.

'I'he operation of my device. is apparent from the foregoing, but tosummarize the operation: pieces or lumps of from one totwo inches indiameter prepared by a suitable method are .placed in a hopper I' andare conveyed therefrom into the feeding mouth` I0 by means oi' theconveyor 56 then through the mechanically operated swinging valves IIand I2 which o'pl erate so as to-isolate free air communication to themill, these lead pieces are fed into the mill 5.

The diameter oi' the mill should be about 62" and' it should lbe about"80" long.- 'I'he lead lumps are `fed lthrough an internally screwthreadedtrunnion 'I and'while'rotating said mill containing about 3,000to 6,000 pounds of lead.

a lumps at a rate of about A40 R. P. M., and feeding 500 to 800 lbs. oflead lumps Vper hour, a small amount of, airnecessaryfi'ox'L blown-throughfthe auxiliary supply pipes 2. and 3 during theA initial period,so as to develop enough heat due to the friction of the lead lumps andalso dueto oxidation of thelead, to bring v pass pipe I8 then throughthe up the'mill temperature to the desired ldegree la ge amount of aircan be taken from the byentire product v collecting system. including 28and Zlothrwise the une reactive powder may laccumulate within the systemdue to the slow current of air-nowing out from the mill which carriessuch powder. When the mill temperature raches thedesired higher degreemore air supplied through the auxiliary pipe. 2 and nozzles lithenstarts to pass' airinto the mill through the main line I, .from .the fan21, throughthe nozzle branches 23.

Under) normal working conditions the amount of air used through'theauxiliary supply line 'I8 ranges from 50 cu. ft. to 200 cu.- ft., perminute, while the amount from the main air line I ranges from 100 to 700cubic feet per minute. 'I'he amount should vary according-to the roomtemperature lwhich varies considerably4 during thex season, in order tokeep the 'mill temperature uniformfa'tthe desiredfrange according toitsstops its operation and l 's nal product.

bags and at the same tached'to the extra air 'supplyline I'I opened soas to blow out the line powderafter it is separaobjective product. Itthe mill temperature kept under 176 F. while suillcient air is passedthrough, a product of metallic lead` powder containing avery smallamount of lead suboxide will be 'produced while beyond that point up toabout 280 F. the

product will consistma'inly of lead suboxide powder containing a verysmall amount oiA metallic lead and possibly a slight amount of leadoxide PbO, but beyond said 280 F. to about 400 F., or higher, a product/mainly consisting of litharge containing a minor portion containingpossibly an amount of litharge will.

be'produced. The art of the process is to control the temperature of themill and adjust the amount of air so as to control the time duration ofproducing the powder staying in the mill due to the effective regulationof blowing power of said air. current. Thus according to the conditionof control for-the mill temperature and air current all ranges ofproducts or a mixture of the above mentioned product can be manufacturedat will. Under fairly controlled conditions Ava product of 500 to 800lbs. or'a slightly greater amount lthan the rated charge per h'our beingproduced per hour.

The product thus blown out from the mill 5 through .the dischargevoutlet pipe 26 is passed int'o the product collectors 28 and separatedfrom the air by means of dust bags 29 and while the air is dischargedthrough the fan 30 the sepa- `rated oxide product is collected into'thewater cooled screw conveyor I3 then discharged through a rotary lockinto la suitable receptacle as a At frequent intervals the shut-oilvalves '30 in the branch pipe, outlet pipe '26 from nately closed duringthe shaking of said dust time a valve 39, Fig. 1, at-

rated from the air,.thrugh the said b ags which ordinarily tend toaccumulate powder on the lower portion 30 of the two ort-more productcollectors' 28 operate alternately at ideal condition.

During the starting period of operation air is passed through theby-pass pipe I9 so as to give ja suillcient air current throughout theproduct' collector system, the amount of suchvair'is rated 200 to 400cu.'ft. according to the requirements, so as to' operate the collectorsystem 'under' uniform low rate'of temperature, but such'amount. Acan beadjusted by means of the valve i9.

- lDuring the summerperiod when working'. mill temperaturen reachesbeyond 300 F., the air passed into the collector through the by-pasapipe I9 often becomes'insuillcient to cool down s'aid collector systemandin such a 'case a valve 32 is 'provided in the ablesthe drawing ofcold atmospheric air into the said collector 2l. to reduce thetemperature of the system vmoderately so as to cool the product to aconsiderably'lower degree -in comparison to that of air andv productdischarged from'the mill. The suction `fan 30 has enough capacity totake 'care of Vall air-that can be forced or taken into said cullectorand according to the adjustment of the damper 3l provided in its suctionline,- such the collector.` In this way o f Fig. 2, from said dischargethemill 5 should-be altersuction capacity can be regulated to anydesired degree. This extra air throughthe by-pass line and also free airintake are necessary to reduce the collector temperature to below 250 F.so as to avoid any rapid oxidation of the product withto 60 inches inwater so as to meet all necessary requirements. Any type of fan orblower may be used but ordinarily a high pressure blower of double ortriple stage fan is used. The reason is not only to create high staticpressure, but the main idea is to supply such air at the highestpossible temperature so as to give a more effective oxidation reactionon the lead contents in the mill. The air supplied through such multiplestage fan possibly reaches more than 50 F. higher temperature than thatof the atmospheric air and produces most effective results on theoxidation of the lead nateriai. Y.

The present invention is aimed to operate the mill under any desirabletemperature condition automatically controlled and also to adjust themanner of blowing effect so as to obtain a definite product of uniformiineness and collect the discharged product under fairly controlledlower temperature, then discharge the final product freely into areceptacle without causing any further undesirable oxidation orspontaneous combustion into a higher oxide, as above set forth, andsince various modifications of the apparatus and its method of operationmay evidently be made, I do not desire to limit my invention by thedetailed description herein of what Iconsider its best form. V

What I claim is:

l. An apparatus for forming powder from lumps of material comprising arevolving 'tumbler mill having feed and exhaust passages, means to forceair through the feed passage to blow the formed-powder out of thel millthrough the exhaust passage, said means including forwardly directednozzles longitudinally spaced apart within A the feed passage, means toreceive the lumps, means to feed the lumps of material into the millthrough the said feed opening, said feeding means being adapted to feedthe material to the mill in a manner to prevent the air from backing outfrom said mill through said feed means and a separate auxiliary airfeeding means for feeding air through said feeding means into the mill.

2. A revolving tumbler mill having an entrance opening and an outlet, ahollow conveyor for delivering material to be pulverized through theentrance opening, and anair pipe extending through the hollow conveyorto supply air to the mill and a second air pipe extending through saidhollow conveyor into the interior of the mill and having a numberofnozzles to supply air to oxidize the material and blow it out of saidoutlet.

3. A pulverizing mill having an outlet, a collector chamber open at itstop, a pump for drawing air through the mul-1nd chamber, fabric bags forltraining`\ the material from the al1 said collector chamber having avalved inlet com y municating with the atmosphere and means to conductthe'incoming air to the lower ends of and to' the outside ofsaid fabricbags to periodithan 1000 cally dislodge the powder settled on theoutside of said bag.

4. A pulverizing mill comprising a rotary tumbler drum and a collectingchamber, said drum having inlet and outlet pipes, the outlet pipeleading to the collecting chamber, the inlet pipe having nozzlesextending angularly therefrom and longitudinally spaced apart thereonwithin the mill, and a handle connected to said inlet pipe whereby itmay `be operated to oscillate said nozzles, a pump for forcing airthrough said pipes and nozzles, a branch pipe in communication with theinlet pipe, said branch pipe extending outside the mill and connected to.said outlet pipe near its union with the collecting chamber and havingnear said union a valved branch pipe open to the atmosphere whereby theproduct islowered in temperature before it enters the collectingchambers and within said chamber.

5. A mill for forming lead oxides from lumps of lead, comprising arevolver tumbler mill with valved inlet and outlet pipes, a collectingchamber, a valved pipe connected to said inlet pipe and extending aroundthe mill to the outlet pipe adjacent the collecting chamber and having,adjacent the outlet pipe, a valved branch pipe, open to the atmosphereand means-for forcing air through said pipes, the inlet pipe havingbranch pipes with downwardly pointing nozzles dii acted to cause the airto impinge against the lumps of lead in the mill to blow the formedpowder upwardly and out of the mill.

6. A pulverizing mill comprising, a rotatable mill and a collectingchamber for the material discharged, a hollow tmnnion through whichmaterial to be pulverized is fed, an inlet air pipe also passing throughsaid trunnion, an outlet pipe for the mill, means for forcing airthrough the null and said pipes, a pipe leading 7from the inlet pipe tothe outlet pipe at a point near the collecting chamber and havingmeansfor direct admission of air at a point near its -junction with theoutlet pipe and means for drawing air through the collecting chamber,pipes and mill and a strainer in the collecting chamber for separatingthe material discharged from the mill and the air passed therethrough.

'1. A pulverizing mill comprising a mill having inlet and outlet pipes,a plurality of collecting chambers both connected to said outlet pipeand having longitudinally extending straining bags therein, means fordrawing air through the collecting chambers and means for shutting offthe air from the mill to each chamber and a valved inlet pipe from theatmosphere,^m.eans for conducting the air from the valved inlet pipe tothe outside and bottom of said bags in said collecting chambers wherebyair may be drawn through the collecting chambeis from the mill ordirectly from the atmosphere.

8. A pulverizing mill comprisingv a cylindrical vessel, a feed hopperleading to said vessel, a motor operated feeding device for/,feedingmaterial to the hopper, a valve in the' ho'pper to cut oi! the feed.means operatively connecting said motor and valve and means controlledby the heat generated in the mill to control the motor that operates thefeed and said valves.

9. An apparatus for pulverizing lumps of material and converting thelumps into powder, which comprises a revolving tumbler mill havingtrunnions through one of which is provided a screw propeller to forcethe material to be pulverized through the trunnion and through the othertrunnion the pulverlzed material is discharged, a collecting chamber,means to force air into the mill also passing through the inlet'feedingscrew propeller in the trunnion and direct the air against said lumps toblow the formed powder through the opening in the exhaust trunnion, anda pipe having a valve therein for passing air fromA the source of supplyaround the mill to the outlet pipe at a point adjacent the collectingchamber 'and having, near its connection with the said outlet pipe meansfor admission of outside air to cool `the material in the collectingchamber into which-the powder is fed.

10. An apparatus for forming powder from ylumps of material, comprisinga revolving tumbler mill a feeding passage, anexhaust passage,

the feed passage being annular and its outer ,wall forming a feed screw,means to force air through the feed passage to blow the formed powderout .of the'mill through the'- exhaust passage, saidl means comprisingforwardly directed nozzles longitudinally spaced within the feedpassage, means to.v receive the lumps, means to feed 'the' lumps intothe feed passage, means to prevent the air from backing out from saidmill through said feed means, and a separate auxiliary air feeding meanspassing through said feed passage for feeding air into the mill foradjusting the mill temperature.

11. A pulverlzing mill having air inlet and outlet pipes, the inlet pipebeing rotatably mounted and'having nozzles extending angularly therefromand spaced apart longitudinally of the mill and having a handle outsidethe mill whereby branch extending outside ythe rotates, -a hopper forfeeding into the trunnion and means .for blowing air into the mill,said.

hopper having two valves each having cam means to open and opposingspring means to close it, and

means arranged and adapted to operate said cam means to open said valvesalternately.

13, An apparatus for pulverizing lumps of ma- A terlal and convertingthe lumps into a powder,

which comprises a revolving tumbler mill having trunnions, one of whichconstitutes a screw propeller to force the vmaterial to be pulverizedthrough the trunnion, and through the other trunnion the pulverizedmaterial is discharged,

means passing through the inletscrew-propeller trunnion to force air atpoints longitudinally spaced apart within the mill against said lumps atsaid points to blow the formed powder through.

the opening in theve'xhaust trunnion and a pipe having a valve thereinfor passing air from the source of supply aroundv the mill to acollector chamber into which the air is fed, said pipe havinga valvebranch beyond the mill through which branch air may be drawn, and passedinto said collector chamber, along with the powdered material and airfrom the mill.

4 LYUHO `S.

